Hello everyone here at Cloudy Nights,
My name is Ethan Cane, a newly joined member who has recently discovered the hobby of Binoculars for both terrestrial and astronomical use. I am based in London in the United Kingdom, actually living in the heart of Central London around Warren Street tube station. I mention this just to give those familiar with the area an idea of the skies I have available to me at home. I live on the fifth floor of an apartment block which faces due east with views to the north and south.
I have only been into the hobby for a few months now, but have managed to build what I consider to be a pretty modest little collection of binoculars:
Leica Noctovid 8×42
Leica Noctovid 10×42
Canon 15×50 IS
Nikon 7×50 Prostar
Nikon 10×70 Astroluxe
I’ve previously owned the Canon 10×42 IS WP L but chose to sell it to assist in the purchase of the Leica Noctovid 10×42, I had found these Canon’s on eBay in Mint (minus) condition but decided to let them go since the battery compartment cover was slightly damaged due to the previous owner using a coin to twist open the cover. For those interested to hear, both this model and the Canon 15×50 or even the larger Canon 18×50, there’s no need to use a coin to do so. They open very easily with just simple fingernail twist pressure. Have to say one of my pet peeves is people who don’t look after their equipment and treat them as precision mechanical/optical instruments. Have to actually say that I consider myself as merely the present guardian of all of my high grade equipment with the responsibility to pass them to future generations.
To look after my binoculars collection I use the excellent Billingham Galbin binocular cases. These are in use for the two Noctovid’s and the Canon. For the two Nikon’s I use the original cases supplied. Have to say that I am very lucky thus far to have purchased everything brand new, having paid current retail prices since it’s my intention to never sell, so wanted assurance that each item contains no user induced flaws either in terms of cosmetic and especially optical performance. It’s also nice to have the backing of whatever warranty is available should things need to be repaired.
So with introductions done, I will post my first ever question here on Cloudy Nights. Perhaps one day I will look back in years to come with a fond nostalgia at either how naive I was or how silly the question was? Time will tell.
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I know that binoculars have four main numbers typically advertised. For example a 7×50 binocular has a magnification of 7x and an objective lens size of 50mm which lends it well to wide field of view usage. This use case is also alluded to when considering it may also designate the actual field of view as being 7.3 degrees from which one can derive the other field of view value by multiplying the magnification by these degrees. 7.3 (degrees) * 7x = 51.1 (degrees).
There are however another set of of numbers I have noted of both of the Nikon models, they can be found on the ocular end of the binoculars, printed at the end of the main axel. Please see the attached image. The numbers I refer to are those of “60” and “70” with the tick marks below. I also note that the tick marks are a little more tightly grouped at the “60” end than at the “70” end, however also note two of the tick marks are taller than the others so as to designate logical separators of “5” increments.
My initial assertion is that these numbers simply refer to degrees when adjusting for parallax compensation between the tubes at varying focal lengths?
Can someone who either owns these binoculars or who has more understanding than me chime in to discuss what these number do in fact mean and more specifically how I might make better use fo their presence. To cut a long story short, I want to understand every aspect of my hobby and not simply remain in the dark, although not likely with any of these objective sizes .
Many thanks all for listening and looking forward to being a part of your community. 
